It will probably require removing the carb and giving it a good cleaning. Fuel stabilizers don't work well with ethanol gas, and even when they are used, the carb should be drained. There is a float bowl drain screw on the carb. The first thing I would try is removing the fuel line from the vacuum valve, draining the float bowl (it may already be empty) but open the drain screw to let anything that might be in there out, then close it. Take a tiny funnel, and attach it to the open end of the fuel line going to the carb. Fill the carb with Seafoam. Now crank the engine. This is to suck the Seafoam up into the jets. The engine may fire, even run a few seconds on the Seafoam, and make black smoke. This will not hurt anything. Seafoam contains naptha, so it will ignite in an engine. I would try this procedure several times before giving up and taking the carb apart. It has worked quite often. After the engine is running good, put some Seafoam in the gas, and run a couple tankfuls of gas with Seafoam in it through the engine. You will probably have to remove some of the bodywork to get to the carb/fuel hose. I believe I got to it by removing the left side panel, but that was a few years ago, not sure now.